As was stated first and foremost, check your gascap. Remove and reseat the gas cap. This is one of the most common CEL causes. Go ahead and use your scan tool and post the code back, we can at least let you know what the cause was.

To put the car in on mode, press the bottom of the rocker switch like you were putting it in to accessory mode but hold the rocker down for about 7 seconds, this will put the car into on mode with engine off.

As was stated first and foremost, check your gascap. Remove and reseat the gas cap. This is one of the most common CEL causes. Go ahead and use your scan tool and post the code back, we can at least let you know what the cause was.

To put the car in on mode, press the bottom of the rocker switch like you were putting it in to accessory mode but hold the rocker down for about 7 seconds, this will put the car into on mode with engine off.

As was stated first and foremost, check your gascap. Remove and reseat the gas cap. This is one of the most common CEL causes. Go ahead and use your scan tool and post the code back, we can at least let you know what the cause was.

To put the car in on mode, press the bottom of the rocker switch like you were putting it in to accessory mode but hold the rocker down for about 7 seconds, this will put the car into on mode with engine off.

Well......the ports won't marry.
The scan's pin port will not marry up with the din under the dash.

It connects to my other Non-GM vehicles.

Guess it's a trip to the dealer Wednesday.
According to the OM, I can drive it as long as it doesn't go into
"Flashing Mode" I think it referenced. Of course it won't be going
out until trip to dealer.

Thanks everyone for your input and help.

At least I have learned how to put it into "Run Mode" w/out
starting it.

Everyone of you have a Very Merry Christmas and the Best to You and
Yours for the New Year.

Well......the ports won't marry.
The scan's pin port will not marry up with the din under the dash.

It connects to my other Non-GM vehicles.

Guess it's a trip to the dealer Wednesday.
According to the OM, I can drive it as long as it doesn't go into
"Flashing Mode" I think it referenced. Of course it won't be going
out until trip to dealer.

Thanks everyone for your input and help.

At least I have learned how to put it into "Run Mode" w/out
starting it.

Everyone of you have a Very Merry Christmas and the Best to You and
Yours for the New Year.

Terry in Tennessee

That's a bummer Terry. Merry Christmas to you. Good luck with the diagnostics and do post back what you find out.

CEL is a problem? Mine's been on for 3 months or more. OnStar has sent me my usual email reports saying everything is OK. I just always figured it is on because I've had a tune. In fact, my tuner checked it out and said don't worry about it